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Related Concept Videos

Homeostatic Imbalances in Body Temperature01:19

Homeostatic Imbalances in Body Temperature

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Hyperthermia occurs when the body's temperature becomes unusually high, often due to heat exposure, intense physical activity, or certain illnesses. This condition can create a dangerous cycle where elevated body temperature increases the metabolic rate, generating more heat and potentially leading to organ failure and brain damage. A severe form of hyperthermia, called heat stroke, can raise body temperature to life-threatening levels. Fever, on the other hand, is a controlled form of...
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Increased Body Temperature01:25

Increased Body Temperature

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A body temperature above  38°C  (100.4 °F) is known as fever or pyrexia, and a person with fever is termed 'febrile.' Typically, the hypothalamus, a part of the brain that acts as the body's thermostat, regulates body temperature through a thermoregulatory setpoint. It receives signals from cold and warm thermal receptors throughout the body and adjusts the body's temperature accordingly. Fever occurs when this hypothalamic setpoint is altered, usually in...
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Thermoregulation01:26

Thermoregulation

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The human body has a sophisticated thermoregulation system that employs negative feedback mechanisms to maintain an optimal core temperature. When the core temperature drops, peripheral and central thermoreceptors send signals to the hypothalamus, activating the heat-promoting center. This center triggers several responses aimed at increasing the core temperature. First, vasoconstriction reduces the flow of warm blood from internal organs to the skin so that the heat is not lost from the skin,...
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Body Temperature01:25

Body Temperature

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The body's temperature, measured in degrees, is determined by the balance between heat production and dissipation to the surrounding environment. For instance, if exercising vigorously, the body will produce more heat, causing sweat and dissipating that heat. Despite extreme environmental conditions and physical exertion, the human temperature-control system maintains a constant core body temperature (the temperature of deep tissues, which are the tissues located beneath the skin and other...
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Body Temperature01:07

Body Temperature

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Body temperature reflects the equilibrium between heat production and heat loss within the body. Most heat is generated by metabolically active tissues, particularly the liver, heart, brain, kidneys, and endocrine organs. At rest, skeletal muscles contribute 20–30% of total heat production, but during vigorous exercise, this can increase up to 30–40 times.
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Mechanism of heat transfer01:19

Mechanism of heat transfer

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Understanding heat transfer mechanisms is essential for understanding how our bodies maintain balance in different environmental conditions. When the environment is thermoneutral, the body is in a state of balance, neither using nor releasing energy to maintain its core temperature. However, when the environment is not thermoneutral, the body employs four heat transfer mechanisms to maintain homeostasis: conduction, convection, evaporation, and radiation. These mechanisms facilitate heat...
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Updated: Nov 30, 2025

Esophageal Heat Transfer for Patient Temperature Control and Targeted Temperature Management
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Hyperthermia reduces electromechanical delay via accelerated electrochemical processes.

Adèle Mornas1,2, Sébastien Racinais1,3, Franck Brocherie1

  • 1French Institute of Sport (INSEP), Laboratory Sport, Expertise and Performance, Paris, France.

Journal of Applied Physiology (Bethesda, Md. : 1985)
|November 12, 2020
PubMed
Summary

Hyperthermia shortens electromechanical delay (EMD) by speeding up electrochemical processes in the gastrocnemius medialis muscle. Mechanical components of force transmission remain unaffected by heat exposure.

Keywords:
contractile propertiesforce transmissionmuscle fascicle motionmuscle temperature

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Area of Science:

  • Exercise Physiology
  • Muscle Physiology
  • Biophysics

Background:

  • Electromechanical delay (EMD) represents the time lag between electrical stimulation and force production in muscles.
  • Understanding the components of EMD (electrochemical and mechanical) is crucial for interpreting muscle function under various physiological conditions.
  • The effects of hyperthermia on the distinct phases of EMD are not fully elucidated.

Purpose of the Study:

  • To investigate the impact of hyperthermia on the electrochemical (Dm) and mechanical (Tm) components of EMD.
  • To determine if heat exposure alters the timing of muscle fascicle motion relative to stimulation and force onset.

Main Methods:

  • Very-high-frame-rate ultrasound was employed to assess EMD components in 16 participants.
  • Measurements were taken in both a control (26°C) and a hot (46-50°C) environment.
  • Electrically evoked peak twitch force, EMD, Dm, and Tm were quantified.

Main Results:

  • Hyperthermia significantly reduced overall EMD (10.8 ± 0.6 ms in CON vs. 9.4 ± 0.8 ms in HOT).
  • The electrochemical component (Dm) was significantly shorter in the hot condition (5.5 ± 0.9 ms in CON vs. 4.0 ± 0.8 ms in HOT).
  • The mechanical component (Tm) of EMD remained unchanged between the hot and control environments (P = 0.622).

Conclusions:

  • Hyperthermia accelerates muscle contraction by speeding up electrochemical processes, leading to a reduced EMD.
  • Force transmission through the series elastic component (aponeurosis and tendon) is not affected by acute heat exposure.
  • These findings highlight that heat primarily impacts the excitation-contraction coupling phase rather than passive force transmission properties.